Diesel oxidation catalysts (DOC) placed in the exhaust flow path of diesel-powered engines are known to treat the exhaust of diesel engines before venting to the atmosphere in order to convert noxious pollutants such as hydrocarbon and carbon monoxide by catalyzing the oxidation of these pollutants to carbon dioxide and water.
The diesel oxidation catalyst activity generally increases with temperature. For diesel oxidation catalysts a threshold temperature is necessary for the diesel oxidation catalyst to “light-off” and convert the noxious gases by oxidation. The “light-off temperature” is defined as the temperature at which 50 mol % of present HC-compounds are catalytically converted. It is important for a diesel oxidation catalyst to reach the necessary working temperature as soon as possible after a cold starting in order to work properly.
The light-off behaviour and performance of a catalyst not only is a function of catalytic formulation and coating density but also of operating conditions. The most significant shift in the light-off temperature occurs with the age of the diesel oxidation catalyst, as the light-off temperature increases with age. Usually, the onboard system of a motor vehicle is adjusted to that on the basis of the assumption of a completely aged diesel oxidation catalyst which leads to a high light-off temperature.
It is a disadvantage that the shift in light-off temperature of aging diesel oxidation catalysts is not sufficiently considered in the motor vehicle.
It is at least one object of the invention to provide a device or means for monitoring the light-off temperature of a diesel oxidation catalyst considering an aging of the diesel oxidation catalyst.